Along with the trends toward high performance, high speed, low power consumption and high integration semiconductor devices, a recess channel transistor has been proposed to improve characteristics of a transistor.
In an attempt to overcome a reduction in the channel length due to shrinkage of device, the recess channel transistor may be configured to secure a sufficiently large channel length by forming a recess trench in a potential region of a transistor channel. In particular, since a high voltage transistor should withstand a high voltage characteristic, advantageous electrical characteristics of the high voltage transistor can be maintained by adopting a recess channel transistor providing a relatively large channel length even in a case where a width of a high-voltage gate is reduced.
In fabricating a high-voltage transistor and a low-voltage transistor using a single process, an insulating film for a high voltage is formed in a recess trench of the high-voltage transistor, and an insulating film for a low voltage is additionally formed in the low-voltage transistor. However, in this case, stress may be applied to an active region of the low-voltage transistor.